Answer:
He was never satisfied <em><u>even though</u></em> he was one of the richest men in the world.
Explanation:
"Even though" is a subordinating conjunction that is used to introduce a statement that is surprising or unexpected. It is also used to present a stronger emphasis on the concerned statements.
The given sentence presents two parts or qualities of a person. The first states how he's never satisfied while the second states the contrast with the first.
Therefore, using "even though" in between the two statements will present the contrasting yet unexpected statement about the person.
In using the subordinating conjunction "even though", the statement that "he's never satisfied" is contrasted with the other statement "he's one of the richest men in the world". His richness does not seem to make him satisfied, which seems unexpected, in most people's opinion as we tend to think money can make us happy.
Thus, the correct sentence structure will become-
<u><em>He was never satisfied even though he was one of the richest men in the world.</em></u>
